> Twitter redirects links through its t.co link-shortening service. It was once a useful addition to its service as it helped people stay underneath the strict character limits. The link shortener reduced all links to 23 characters. Twitter gains some more data-insights about its users in the form of click-stream data and insight into popular links.

The t.co link also helps them block URLs that they deem problematic on their platform - in the event of spam, attack, or abuse, the redirect can instead be a black hole.